diff --git a/package.json b/package.json
index a0c63fadf3f..7cf074f2ec5 100644
--- a/package.json
+++ b/package.json
@@ -227,7 +227,7 @@
     "@parcel/watcher": "^2.5.6",
     "@xterm/addon-serialize": "0.15.0-beta.301",
     "@xterm/headless": "6.1.0-beta.303",
-    "agent-browser": "~0.27.3",
+    "agent-browser": "~0.39.4",
     "electron-updater": "^6.8.10",
     "fflate": "0.8.3",
     "i18next": "^26.5.11",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 9f3762426fb..a54699ff06d 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -216,8 +216,8 @@ importers:
         specifier: 6.1.0-beta.303
         version: 6.1.0-beta.303
       agent-browser:
-        specifier: ~0.27.3
-        version: 0.27.3
+        specifier: ~0.39.4
+        version: 0.39.4
       electron-updater:
         specifier: ^6.8.10
         version: 6.8.10(electron@43.8.1(supports-color@7.2.0))(supports-color@7.2.0)
@@ -480,12 +480,12 @@ importers:
       hast-util-from-html-isomorphic:
         specifier: 2.0.0
         version: 2.0.0
-      hast-util-to-text:
-        specifier: 4.0.2
-        version: 4.0.2
       hast-util-to-jsx-runtime:
         specifier: 2.3.6
         version: 2.3.6(supports-color@7.2.0)
+      hast-util-to-text:
+        specifier: 4.0.2
+        version: 4.0.2
       html-to-image:
         specifier: ^1.11.13
         version: 1.11.13
@@ -4423,8 +4423,8 @@ packages:
     resolution: {integrity: sha512-MnA+YT8fwfJPgBx3m60MNqakm30XOkyIoH1y6huTQvC0PwZG7ki8NacLBcrPbNoo8vEZy7Jpuk7+jMO+CUovTQ==}
     engines: {node: '>= 14'}
 
-  agent-browser@0.27.3:
-    resolution: {integrity: sha512-isQ1xWoYOnfR8BigYRlYmkFOrqw71tKEmUEMmFJGStQFOyCrLSsKoOAZEu8TjPZdmjD1nPQ/hLLYlxTwdHnA0Q==}
+  agent-browser@0.39.4:
+    resolution: {integrity: sha512-R0ue5CWlpkGtbcXeq3ZKM96zLrCXkNKEGyttgWhi0eSNKoNSvxglvv1/D9NhKxe+MI+djiCFepPd4PYOM0H2Rg==}
     engines: {node: '>=24.0.0', pnpm: '>=11.0.0'}
     hasBin: true
 
@@ -4432,9 +4432,12 @@ packages:
     resolution: {integrity: sha512-8iUql50EUR+uUcdRQ3HDqa6EVyo3docL8g5WJ3FNcWmu62IbkGUue/pEyLBW8VGKKucTPgqeks4fIU1DA4yowQ==}
     peerDependencies:
       '@types/ajv': '*'
+      ajv: ^8.0.0
     peerDependenciesMeta:
       '@types/ajv':
         optional: true
+      ajv:
+        optional: true
 
   ajv@6.15.0:
     resolution: {integrity: sha512-fgFx7Hfoq60ytK2c7DhnF8jIvzYgOMxfugjLOSMHjLIPgenqa7S7oaagATUq99mV6IYvN2tRmC0wnTYX6iPbMw==}
@@ -8839,7 +8842,7 @@ snapshots:
     dependencies:
       '@hono/node-server': 2.1.0(hono@4.13.11)
       ajv: 8.20.0
-      ajv-formats: 3.0.1
+      ajv-formats: 3.0.1(ajv@8.20.0)
       content-type: 1.0.5
       cors: 2.8.6
       cross-spawn: 7.0.6
@@ -11137,10 +11140,10 @@ snapshots:
 
   agent-base@7.1.4: {}
 
-  agent-browser@0.27.3: {}
+  agent-browser@0.39.4: {}
 
-  ajv-formats@3.0.1:
-    dependencies:
+  ajv-formats@3.0.1(ajv@8.20.0):
+    optionalDependencies:
       ajv: 8.20.0
 
   ajv@6.15.0:
diff --git a/src/main/browser/agent-browser-batch-command.ts b/src/main/browser/agent-browser-batch-command.ts
index 64bc8a6c5c0..b5f745bf0ee 100644
--- a/src/main/browser/agent-browser-batch-command.ts
+++ b/src/main/browser/agent-browser-batch-command.ts
@@ -14,8 +14,27 @@ export function parseAgentBrowserJsonOutput(stdout: string): AgentBrowserEnvelop
   const parsed = JSON.parse(stdout)
   // Orca batches one command; a longer array is a passthrough `exec batch` reply.
   if (!Array.isArray(parsed) || parsed.length !== 1) {
-    return parsed
+    return withoutDaemonLifecycle(parsed)
   }
   const [entry] = parsed
-  return { success: entry?.success, data: entry?.result, error: entry?.error }
+  return withoutDaemonLifecycle({
+    success: entry?.success,
+    data: entry?.result,
+    error: entry?.error
+  })
+}
+
+// agent-browser 0.31+ adds its daemon's launch bookkeeping to every reply; it is not page data.
+function withoutDaemonLifecycle(envelope: AgentBrowserEnvelope): AgentBrowserEnvelope {
+  const data = envelope?.data
+  if (!data || typeof data !== 'object' || Array.isArray(data) || !('lifecycle' in data)) {
+    return envelope
+  }
+  const { lifecycle: _lifecycle, ...rest } = data
+  return { ...envelope, data: rest }
+}
+
+/** "Unknown ref" for a ref never issued; 0.39+ also says "Stale ref for role=…" once its element is gone. */
+export function isAgentBrowserStaleRefError(message: string): boolean {
+  return /unknown ref|stale ref|ref not found|element not found: @e/i.test(message)
 }
diff --git a/src/main/browser/agent-browser-bridge-command-transport.test.ts b/src/main/browser/agent-browser-bridge-command-transport.test.ts
index 111f8e3a1d1..3e838bdaf11 100644
--- a/src/main/browser/agent-browser-bridge-command-transport.test.ts
+++ b/src/main/browser/agent-browser-bridge-command-transport.test.ts
@@ -202,6 +202,22 @@ describe('AgentBrowserBridge', () => {
     await expect(bridge.snapshot()).rejects.toThrow('Command failed')
   })
 
+  it('drops the daemon lifecycle agent-browser adds to every result', async () => {
+    // Real agent-browser 0.39.4 batch reply.
+    const reply =
+      '[{"command":["click","@e2"],"error":null,"result":{"clicked":"@e2","lifecycle":{"effectiveLaunch":{"browserLaunched":true,"engine":"chrome","launchHash":520248349195465926},"launched":false,"relaunchedBrowser":false,"restartedBackground":false,"restoreStatus":"not_configured","reused":true,"saveStatus":"not_attempted"}},"success":true}]'
+    answerAgentBrowserCommands(execFileMock, stdinWrites, (_command, cb) => cb(null, reply, ''))
+    await expect(bridge.click('@e2')).resolves.toEqual({ clicked: '@e2' })
+  })
+
+  it('reports a ref whose element is gone as stale', async () => {
+    // agent-browser 0.39.2+ wording when it cannot re-resolve a ref by role and name.
+    failWith(
+      'Stale ref for role=button name=Approve cannot be recovered: several elements now match. Run snapshot again and use a fresh ref.'
+    )
+    await expect(bridge.click('@e2')).rejects.toMatchObject({ code: 'browser_stale_ref' })
+  })
+
   it('returns browser_error with truncated output for malformed JSON', async () => {
     execFileMock.mockImplementation(
       (_bin: string, _args: string[], _opts: unknown, cb: ExecFileCallback) => {
diff --git a/src/main/browser/agent-browser-bridge-process.ts b/src/main/browser/agent-browser-bridge-process.ts
index 70c097244d7..275c3f8a9ed 100644
--- a/src/main/browser/agent-browser-bridge-process.ts
+++ b/src/main/browser/agent-browser-bridge-process.ts
@@ -1,11 +1,13 @@
 import { app } from 'electron'
-import { existsSync, accessSync, chmodSync, constants } from 'node:fs'
+import { existsSync } from 'node:fs'
 import { join } from 'node:path'
 import { platform, arch } from 'node:os'
 import type { WebContents } from 'electron'
 import { BrowserError } from './cdp-bridge'
 import { ORCA_TAB_SESSION_PREFIX } from './agent-browser-orphan-sweep'
 import { EMBEDDED_NAVIGATION_TIMEOUT_MS } from './agent-browser-bridge-types'
+import { ensureDependencyBinaryExecutable } from './agent-browser-dependency-binary'
+import { isAgentBrowserStaleRefError } from './agent-browser-batch-command'
 
 export function agentBrowserNativeName(): string {
   const ext = process.platform === 'win32' ? '.exe' : ''
@@ -33,13 +35,7 @@ export function resolveAgentBrowserBinary(): string {
     agentBrowserNativeName()
   )
   if (existsSync(nmBin)) {
-    if (process.platform !== 'win32') {
-      try {
-        accessSync(nmBin, constants.X_OK)
-      } catch {
-        chmodSync(nmBin, 0o755)
-      }
-    }
+    ensureDependencyBinaryExecutable(nmBin)
     return nmBin
   }
 
@@ -91,7 +87,7 @@ export function stripAgentBrowserTargetArgs(args: string[]): string[] {
 
 // Stale refs need a distinct code so agents can retry with a fresh snapshot.
 export function classifyErrorCode(message: string): string {
-  if (/unknown ref|ref not found|element not found: @e/i.test(message)) {
+  if (isAgentBrowserStaleRefError(message)) {
     return 'browser_stale_ref'
   }
   return 'browser_error'
diff --git a/src/main/browser/agent-browser-dependency-binary.ts b/src/main/browser/agent-browser-dependency-binary.ts
new file mode 100644
index 00000000000..18bce0e27f1
--- /dev/null
+++ b/src/main/browser/agent-browser-dependency-binary.ts
@@ -0,0 +1,13 @@
+import { accessSync, chmodSync, constants } from 'node:fs'
+
+/** pnpm skips agent-browser's postinstall, which is what marks its tarball binaries executable. */
+export function ensureDependencyBinaryExecutable(path: string): void {
+  if (process.platform === 'win32') {
+    return
+  }
+  try {
+    accessSync(path, constants.X_OK)
+  } catch {
+    chmodSync(path, 0o755)
+  }
+}
diff --git a/src/main/browser/cdp-ws-proxy.test.ts b/src/main/browser/cdp-ws-proxy.test.ts
index 4d16c97ac4a..f94e9f8fdb4 100644
--- a/src/main/browser/cdp-ws-proxy.test.ts
+++ b/src/main/browser/cdp-ws-proxy.test.ts
@@ -340,6 +340,26 @@ describe('CdpWsProxy', () => {
     client.close()
   })
 
+  it('never leaves auto-attached workers and frames waiting on a client that may leave', async () => {
+    mock.webContents.debugger.sendCommand.mockResolvedValueOnce({})
+
+    const client = await connect(endpoint)
+    // agent-browser 0.39 asks child targets to wait for it; the shared guest debugger outlives it.
+    await sendAndReceive(client, {
+      id: 1,
+      method: 'Target.setAutoAttach',
+      params: { autoAttach: true, waitForDebuggerOnStart: true, flatten: true },
+      sessionId: 'oopif-session-123'
+    })
+
+    expect(mock.webContents.debugger.sendCommand).toHaveBeenCalledWith(
+      'Target.setAutoAttach',
+      { autoAttach: true, waitForDebuggerOnStart: false, flatten: true },
+      'oopif-session-123'
+    )
+    client.close()
+  })
+
   it('forwards CDP events from debugger to client', async () => {
     const client = await connect(endpoint)
 
diff --git a/src/main/browser/cdp-ws-proxy.ts b/src/main/browser/cdp-ws-proxy.ts
index fa36662412c..0d3934d09e0 100644
--- a/src/main/browser/cdp-ws-proxy.ts
+++ b/src/main/browser/cdp-ws-proxy.ts
@@ -297,6 +297,12 @@ export class CdpWsProxy {
       void this.navigation.reloadWithLifecycle(client, clientId, msg.params ?? {}, msg.sessionId)
       return
     }
+    // The guest debugger outlives this client, so nothing would resume workers or frames left waiting.
+    if (msg.method === 'Target.setAutoAttach') {
+      const params = { ...msg.params, waitForDebuggerOnStart: false }
+      this.debuggerChannel.forwardCommand(client, clientId, msg.method, params, msg.sessionId)
+      return
+    }
     this.debuggerChannel.forwardCommand(
       client,
       clientId,
diff --git a/src/main/orcad/external-chromium-browser-session.test.ts b/src/main/orcad/external-chromium-browser-session.test.ts
index 0dd02cabdc5..300874fb7de 100644
--- a/src/main/orcad/external-chromium-browser-session.test.ts
+++ b/src/main/orcad/external-chromium-browser-session.test.ts
@@ -93,10 +93,30 @@ describe('orcad external-chromium agent-browser environment', () => {
     }
   )
 
+  it('reports a ref whose element is gone as stale', async () => {
+    runProcessMock.mockResolvedValue({
+      code: 1,
+      signal: null,
+      stdout: JSON.stringify({
+        success: false,
+        error:
+          'Stale ref for role=button name=Approve cannot be recovered: several elements now match.'
+      }),
+      stderr: '',
+      timedOut: false
+    })
+    const session = new ExternalChromiumBrowserSession(
+      '/opt/orca/agent-browser',
+      { executablePath: BASE.executablePath, provider: 'chromium' },
+      '/state'
+    )
+    await expect(session.run(['click', '@e2'])).rejects.toMatchObject({ code: 'browser_stale_ref' })
+  })
+
   it('never bounds the daemon that owns the Chromium tree', () => {
     const env = externalChromiumAgentBrowserEnvironment({ inheritedEnv: {}, ...BASE })
 
-    expect(env.AGENT_BROWSER_IDLE_TIMEOUT_MS).toBeUndefined()
+    expect(env.AGENT_BROWSER_IDLE_TIMEOUT_MS).toBe('0')
     expect(env.AGENT_BROWSER_EXECUTABLE_PATH).toBe(BASE.executablePath)
     expect(env.AGENT_BROWSER_SESSION).toBe(BASE.sessionName)
   })
diff --git a/src/main/orcad/external-chromium-browser-session.ts b/src/main/orcad/external-chromium-browser-session.ts
index c5f89db6d60..0df599dc033 100644
--- a/src/main/orcad/external-chromium-browser-session.ts
+++ b/src/main/orcad/external-chromium-browser-session.ts
@@ -6,6 +6,7 @@ import { BrowserError } from '../browser/browser-error'
 import {
   AGENT_BROWSER_BATCH_ARGS,
   agentBrowserBatchInput,
+  isAgentBrowserStaleRefError,
   parseAgentBrowserJsonOutput
 } from '../browser/agent-browser-batch-command'
 import { BROWSER_UNAVAILABLE_ERROR_CODE } from '../../shared/runtime-types'
@@ -38,7 +39,7 @@ const AgentBrowserEnvelope = z.object({
 export type AgentBrowserTab = z.infer<typeof AgentBrowserTab>
 
 function classifyAgentBrowserError(message: string): string {
-  if (/unknown ref|ref not found|element not found: @e/i.test(message)) {
+  if (isAgentBrowserStaleRefError(message)) {
     return 'browser_stale_ref'
   }
   if (/evaluation error/i.test(message)) {
@@ -57,6 +58,7 @@ function classifyAgentBrowserError(message: string): string {
 }
 
 // No idle timeout: this daemon owns the user’s remote Chromium and all its live tabs.
+// agent-browser 0.33+ reads an unset timeout as one hour, so only "0" keeps it unbounded.
 export function externalChromiumAgentBrowserEnvironment(options: {
   inheritedEnv: NodeJS.ProcessEnv
   executablePath: string
@@ -66,6 +68,8 @@ export function externalChromiumAgentBrowserEnvironment(options: {
 }): NodeJS.ProcessEnv {
   return {
     ...options.inheritedEnv,
+    AGENT_BROWSER_IDLE_TIMEOUT_MS:
+      options.inheritedEnv.AGENT_BROWSER_IDLE_TIMEOUT_MS?.trim() || '0',
     AGENT_BROWSER_EXECUTABLE_PATH: options.executablePath,
     AGENT_BROWSER_PROFILE: options.profilePath,
     AGENT_BROWSER_SESSION: options.sessionName,
diff --git a/src/main/orcad/orcad-agent-browser-binary.ts b/src/main/orcad/orcad-agent-browser-binary.ts
index 932578c4596..833329b1181 100644
--- a/src/main/orcad/orcad-agent-browser-binary.ts
+++ b/src/main/orcad/orcad-agent-browser-binary.ts
@@ -2,6 +2,7 @@ import { accessSync, constants, existsSync } from 'node:fs'
 import { arch, platform } from 'node:os'
 import { dirname, join } from 'node:path'
 import { orcadAgentBrowserNativeName } from '../../shared/orcad-agent-browser-name'
+import { ensureDependencyBinaryExecutable } from '../browser/agent-browser-dependency-binary'
 
 /** A slot carries only its own target's driver, so trying both libc names needs no libc probe. */
 function hostDriverNames(): string[] {
@@ -14,14 +15,17 @@ function hostDriverNames(): string[] {
 
 export function resolveOrcadAgentBrowserBinary(): string | null {
   const candidates = hostDriverNames().flatMap((name) => [
-    join(dirname(process.argv[1] ?? __filename), name),
-    join(process.cwd(), 'node_modules', 'agent-browser', 'bin', name)
+    { path: join(dirname(process.argv[1] ?? __filename), name), dependency: false },
+    { path: join(process.cwd(), 'node_modules', 'agent-browser', 'bin', name), dependency: true }
   ])
-  for (const candidate of candidates) {
+  for (const { path: candidate, dependency } of candidates) {
     if (!existsSync(candidate)) {
       continue
     }
     try {
+      if (dependency) {
+        ensureDependencyBinaryExecutable(candidate)
+      }
       accessSync(candidate, process.platform === 'win32' ? constants.F_OK : constants.X_OK)
       return candidate
     } catch {